Impact of Residential Greeness Exposure on the Development of Allergic Diseases and Asthma and on Asthma Control—A Systematic Review for the EAACI Guidelines of Environmental Science for Allergic Diseases and Asthma

The role of residential greenness exposure (RGE) in prevention and control of allergic diseases remains controversial. This systematic review evaluated the association between RGE and the risk of developing asthma, allergic rhinitis (AR), food allergy, atopic dermatitis (AD), and asthma control. MEDLINE and EMBASE searches retrieved 17 cohort and case–control longitudinal studies (12 for asthma, 6 AR, 1 food allergy, 1 ad). Risk of bias was assessed with ROBINS-E, and certainty of evidence with GRADE. Data were meta-analyzed using adjusted odds ratios (aORs) with random-effects models. For “ever asthma” and “ever AR” a non-significant protective trend of RGE was observed (aOR 0.92, 95% CI 0.72–1.18; aOR 0.61; 95% CI 0.24–1.55). For “current asthma” RGE was associated with increased risk (aOR 1.17, 95% CI 1.04–1.33), with no clear association for “current AR” (aOR 1.03; 95% CI 0.80–1.32). Prenatal RGE reduced the risk of “ever asthma” (aOR 0.94, 95% CI 0.93–0.950) and AD (aOR 0.996, 95% CI 0.993–0.999). RGE increased the risk for peanut (aOR 1.78, 95% CI 1.13–2.82) and egg allergy (aOR 1.38, 95% CI [1.05–1.82]). Reduced RGE decreased asthma control (OR: 2.662, 95% CI [1.043–6.799]). Potential benefits or potential harms of RGE should be judged in a context-specific manner.